Simplify the following expression: $r = \dfrac{a}{a + 8} + \dfrac{-2a + 1}{a + 8}$
Answer: Since the expressions have the same denominator we simply combine the numerators: $r = \dfrac{a - 2a + 1}{a + 8}$ Combine like terms: $r = \dfrac{-a + 1}{a + 8}$